* Republican lawmaker says Obama made "hash" of argument
* Top White House official appears on five Sunday news shows (Adds quotes, details on vote counts)
By John Whitesides and Rachelle Younglai
WASHINGTON, Sept 8 (Reuters) - The White House pressed its case on Sunday for military action in Syria but faced an uphill fight in Congress, where several prominent lawmakers said they have not been persuaded to approve strikes against Syrian President Bashar al-Assad's forces.
With a crucial test vote planned in the U.S. Senate on Wednesday, White House Chief of Staff Denis McDonough made the rounds of five Sunday talk shows to argue that a limited strike in response to the Syrian government's alleged use of chemical weapons would send a message of deterrence.
But Mike Rogers, Republican chairman of the House of Representatives Intelligence Committee and a supporter of the strikes, said President Barack Obama had made "a hash" of his argument for military action to punish Assad.
"It's very clear he's lost support in the last week ... The president hasn't made the case," Rogers said on CBS's "Face the Nation."
Obama's plan faces significant resistance from Republicans and his fellow Democrats in Congress, with many lawmakers worried military strikes in Syria could lead to a prolonged U.S. commitment there and spark broader conflicts in the region.
"I am asking where is the national security issue? Make no mistake about it, the minute that one of those cruise missiles lands in there, we are in the Syrian war," Democratic Representative Loretta Sanchez of California said on NBC's "Meet the Press" program.
"For the president to say this is just a very quick thing and we are out of there, that's how long wars start," said Sanchez, who described herself as "leaning no."
Michael McCaul, Republican chairman of the House Homeland Security Committee, said Obama's plan was "irresponsible."
"The problem is, I think lobbing a few Tomahawk missiles will not restore our credibility overseas. It's kind of a face-saving measure for the president after he drew the red line," McCaul said.
Representative Jim McGovern, a Democrat from Massachusetts, said on CNN's "State of the Union" program that "if I were the president, I would withdraw my request. I don't believe the support is there in Congress."
Congressional surveys make it clear Obama has a difficult task. A Washington Post vote count showed 223 House members either against or leaning against authorizing the use of military force in Syria. That is more than the 217 needed to block the resolution.
There are still large blocs of undecided lawmakers, however, and McDonough said it was "too early to come to any conclusions" about the eventual outcome in Congress. But several lawmakers said the White House was fighting a losing battle.
"I just wish the president had laid this out better, I wish he'd quit backing away from his own red line and I wish he was more of a commander in chief than a community organizer," said Republican Representative Peter King of New York, who said he would vote yes "in spite of the president's conduct."
The chairman of the House Armed Services Committee said that given the cuts to the military budget in recent years, the added cost of the operation in Syria could hurt military readiness. "If we can fix this, it may help some people in their vote," Republican Buck McKeon said on CNN.
McDonough led the administration's lobbying effort on Sunday, and it will continue on Monday when Obama sits for six network television interviews and national security adviser Susan Rice speaks on Syria in Washington.
More bipartisan briefings are set, and McDonough will meet with Democrats in the House before Obama caps the push with a national address from the White House on Tuesday night.
"Are there consequences for a dictator who would have used those weapons to gas to death hundreds of children? The answer to that question ... will be followed closely in Damascus, but will also be followed closely in Tehran, among Lebanese Hezbollah, and others. So this is a very important week," McDonough said on the "Fox News Sunday" program.
Assad pushed back against Obama on Sunday, denying that his government was behind the chemical weapons attack in Syria and arguing the evidence was not conclusive that such an attack occurred.
"There has been no evidence that I used chemical weapons against my own people," CBS reported Assad said in an interview conducted in Damascus.
McDonough said it was "common sense" that Assad was responsible for the attacks.
"Now do we have irrefutable, beyond reasonable doubt evidence? This is not a court of law, and intelligence does not work that way," McDonough said on CNN.
U.S. Secretary of State John Kerry, speaking in Paris after meeting key Arab foreign ministers, did not rule out returning to the U.N. Security Council to secure a Syria resolution once U.N. inspectors complete a report on a chemical weapons attack but said Arab countries wanted a tough response. (Reporting by John Whitesides and Rachelle Younglai; Additional reporting by David Brunnstrom, Jason Lange and Eric Beech; Editing by Jackie Frank and Eric Beech)